osg中如何将两个geonetry重叠的部分不绘制
时间: 2024-02-26 18:59:31 浏览: 17
要在osg中将两个重叠的geometry的重叠部分不绘制,可以使用以下方法:
1. 将两个geometry添加到同一个osg::Geode中,并设置它们的渲染顺序,确保后添加的geometry在前添加的geometry之前绘制。
2. 使用osg::Stencil两次渲染来实现。第一次渲染时,将stencil buffer设为只有在后添加的geometry的区域中写入1,其余区域写入0。第二次渲染时,将stencil buffer设为只有在前添加的geometry的区域中值为0的区域才能绘制,即后添加的geometry覆盖的区域不再绘制。
下面是示例代码:
```
// 创建两个geometry
osg::ref_ptr<osg::Geometry> geom1 = createGeometry1();
osg::ref_ptr<osg::Geometry> geom2 = createGeometry2();
// 创建osg::Geode,并将两个geometry添加到其中
osg::ref_ptr<osg::Geode> geode = new osg::Geode();
geode->addDrawable(geom1.get());
geode->addDrawable(geom2.get());
// 设置渲染顺序
geode->getOrCreateStateSet()->setRenderBinDetails(0, "RenderBin");
// 创建一个osg::Stencil状态,并设置为只在后添加的geometry的区域中写入1
osg::ref_ptr<osg::Stencil> stencil = new osg::Stencil();
stencil->setFunction(osg::Stencil::ALWAYS, 1, 0xffffffff);
stencil->setOperation(osg::Stencil::KEEP, osg::Stencil::KEEP, osg::Stencil::REPLACE);
geode->getOrCreateStateSet()->setAttributeAndModes(stencil.get(), osg::StateAttribute::ON);
// 第一次渲染,将后添加的geometry的区域写入1
osg::ref_ptr<osg::Camera> camera1 = createCamera();
camera1->setClearMask(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
camera1->setRenderOrder(osg::Camera::PRE_RENDER);
camera1->attach(osg::Camera::STENCIL_BUFFER, GL_STENCIL_ATTACHMENT_EXT);
camera1->addChild(geode.get());
osg::ref_ptr<osg::Group> group1 = new osg::Group();
group1->addChild(camera1.get());
osgUtil::CullVisitor cullVisitor;
cullVisitor.setTraversalMask(osg::CullSettings::ALL_VARIABLES & ~osg::CullSettings::CULL_DISABLED);
group1->accept(cullVisitor);
// 第二次渲染,将前添加的geometry的区域中值为0的区域才能绘制
osg::ref_ptr<osg::Stencil> stencil2 = new osg::Stencil();
stencil2->setFunction(osg::Stencil::EQUAL, 0, 0xffffffff);
stencil2->setOperation(osg::Stencil::KEEP, osg::Stencil::KEEP, osg::Stencil::KEEP);
geode->getOrCreateStateSet()->setAttributeAndModes(stencil2.get(), osg::StateAttribute::ON);
osg::ref_ptr<osg::Camera> camera2 = createCamera();
camera2->setClearMask(GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
camera2->setRenderOrder(osg::Camera::POST_RENDER);
camera2->addChild(geode.get());
osg::ref_ptr<osg::Group> group2 = new osg::Group();
group2->addChild(camera2.get());
group2->addChild(group1.get());
group2->accept(cullVisitor);
```
其中,createGeometry1()和createGeometry2()是创建两个geometry的函数,createCamera()是创建相机的函数。在渲染时,首先使用第一个Camera将后添加的geometry的区域中写入1,并将stencil buffer附加到相机上;接着使用第二个Camera将前添加的geometry的区域中值为0的区域才能绘制。通过这种方式,就可以实现在osg中将两个geometry重叠的部分不绘制。